The moon and Earth may be more different than long thought, challenging existing models for how the moon formed, a new study finds. //

The moon and Earth may be more different than previously thought, challenging existing models for how the moon formed, a new study finds.

Earth originated about 4.5 billion years ago, and previous research suggested that the moon arose a short time after that. For the past three decades, the prevailing explanation for the moon's origin was that it resulted from the collision of two protoplanets, or embryonic worlds. One of those was the newborn Earth, and the other was a Mars-size rock nicknamed Theia, after the mother of the moon in Greek myth. "Once the dust settled, two bodies were left — Earth and the moon," new study co-author Zachary Sharp, a planetary scientist at the University of New Mexico in Albuquerque, told Space.com.